Tangential or cross-flow filtration cassettes are generally known in the art and are typically used to filter materials in a variety of industries including biotechnology and the food and beverage industries. Filtration cassettes are stacked assemblies made up of a plurality of layers comprising filtrate and retentate flow screens and intermediary porous membranes. These layers are stacked and compressed between top and bottom frame elements. A suspension fluid is introduced into a cassette through one or more portals, which then flows across a porous member whereby the some of the material, the filtrate, seeps downward through the member and the remaining material, the retentate, flows into and out of that layer of the cassette through a portal typically on the opposite side of the porous member layer. The filtrate that passes through the porous membrane flows out or is drained through a filtrate port. A cassette typically contains several layers which must each be fluid sealed from their respective adjacent layers. Currently, this seal is achieved through a variety of time consuming processes and with less then optimal materials.
There are several problems associated with these current materials and methods. Most of these methods involve a multi-step process that is time consuming and costly. For example, a typical multi-step process involves sealing the unused ports in a given individual layer while binding the membrane to the flow screens. This step includes arranging the flow screens and membrane into a fixture and then introducing the sealing materials under a vacuum. Next, the subassemblies are manually stacked within a frame or mold and a resin is then introduced around the outside surfaces of the stacked assembly, again under a vacuum. The entire assembly is then compressed between end plates to seal all the components together.
Other methods, although somewhat improved in terms of their cost and the efficiency of manufacture, do not provide a sufficient seal between the layers or degrade overtime.
For example, multi-component resin systems generally leach the constituents of the systems. Two-part resin systems are inherently unclean because their constituent parts do not completely or uniformly mix together. The unmixed constituents of the resin systems therefore leach over time from the cured encapsulant. These leachables are troublesome to the end user because the fluid stream typically comprises expensive drug products that require ultra clean conditions.
The current technologies are generally labor intensive to manufacture and therefore more expensive. Given the high cost of current devices, these current devices are usually reused, which compounds the problems caused by their inherently unclean characteristics. Multi-use products generally lead to cross-contamination because the devices are difficult to clean and, even when cleaned, the cleaning attempts inevitably leave behind contaminants causing subsequent cross-contamination between runs.